1. Field of the Invention
The present invention relates to a method of manufacturing a thermal print head.
2. Description of the Related Art
A method of manufacturing a thermal print head can be found in JP-A-2000-118024. According to this document, a glaze layer 92 is first formed on a substrate 91, as shown in FIG. 13 of the present application. This is followed by formation of an electrode 93 and a resistor 94 on the glaze layer 92. Finally a protection layer 95 constituted of glass is provided so as to cover the glaze layer 92, the electrode 93 and the resistor 94.
Upon formation of the protection layer 95, conductivity of the electrode 93 is inspected. When the electrode 93 is disconnected as pointed by numeral 93a in FIG. 13, the disconnected portion is repaired as follows.
As already stated, the glass protection layer 95 is formed after the formation of the electrode 93 (and the resistor 94). Therefore, the disconnected portion 93a is filled with a portion of the protection layer 95 as shown in FIG. 13. For repairing the disconnected portion, the portion of the protection layer present in the disconnected portion is heated. To be more detailed, the filled disconnected portion (i.e. the protection layer 95) contains an oxide of a conductive material. Heating the oxide for deoxidization turns the protection layer in the disconnected portion into a conductor, thereby restoring the conductivity of the disconnected portion of the electrode 93.
FIG. 14 shows another repairing method of the disconnection of the electrode 93. Once the electrode 93 proves to have the disconnected portion 93a, the portion of the protection layer 95 present in the disconnected portion 93a and in the proximity thereof is removed. Then the disconnected portion 93a is filled with a conductor 93b. 
In either of the repairing methods, the disconnected portion 93a is repaired after the formation of the protection layer 95. This incurs a drop in production efficiency. Besides, the method according to FIG. 13 (heating of the protection layer 95) may fail to restore sufficient conductivity. Further, another type of defect may be caused at the electrode 93, including a short circuit of the electrode 93 with another conductor that is supposed to be insulated, for example. A measure has to be also taken against such undue conduction, in order to improve the yield of the product.